Slapper type detonators in general cause a “flying plate” or “flyer layer” to be propelled at a high velocity against a secondary explosive medium creating a shock wave which results in the detonation of the secondary explosive. In a typical design, there are two wide area conductive lands separated by a narrow rectangular bridge member. The lands are connected to a capacitor through a high voltage switch. When the switch closes, the capacitor provides current across the lands which vaporizes the bridge member turning it into a plasma. This plasma accelerates a portion of the dielectric material covering the bridge member, the flying plate or flyer layer, to a high velocity, causing the flying plate or flyer layer to slap into an explosive. The resulting shock wave causes detonation of the explosive. This type of detonator is also known as a “chip slapper detonator.”
FIGS. 1 through 3 show diagrams illustrating the production process for a prior art chip slapper. In FIGS. 1 through 3 the thickness of the relative layers are exaggerated for the purposes of illustration.
Manufacturing may begin with a wafer 60, FIG. 1 which includes a ceramic substrate layer 62, a sticking layer 64, for example, titanium tungsten, a first conductive layer 66, for example, copper, a buffer layer 68, and a second conductive layer 70, for example, a gold coating. The buffer layer 68 may be, for example, a titanium-tungsten composition. The buffer layer 68 may retard or prevent inter-diffusion between copper of the first conductive layer 66 and the second conductive layer 70. Similarly, forming the second conductive layer 70 of gold may promote solder-ability of land areas 42, 44 (FIG. 2).
The wafer 60 may be used to fabricate one or more chip slappers 46. First, for each chip slapper 46, the second conductive layer 70, the buffer layer 68, the copper conductive layer 66, and the sticking layer 64 may be etched as shown in FIG. 2 to form wide land areas (lands) 42 and 44 and a narrow bridge portion 50 spanning between the lands 42, 44. In FIG. 2, only one chip slapper 46 is shown but it is to be understood that wafer 60, (FIG. 1) may be used to produce a number of chip slappers 46 as shown in FIG. 2.
After the lands 42, 44 and the bridge 50 have been etched, the second conductive layer 70 is etched off the bridge portion 50 to expose buffer material 68 as shown in FIG. 3. A non-conductive flyer layer, for example, a dielectric coating such as polyimide or Kapton® layer, 52 is secured to the bridge portion 50 of each chip slapper 46. Each individual chip slapper 46 may be cut from the wafer 60 (FIG. 1).
Thus, the chip slapper 46 includes a substrate 54 formed of the ceramic substrate layer 62, the sticking layer 64 on the substrate 54, the conductive layer 66 on the sticking layer 64 in the shape of lands 42 and 44 separated by a bridge portion 50 between the lands 42 and 44. In alternative embodiments, the substrate 54 may be formed of other materials, for example, sapphire, silicon nitride, synthetic diamond, beryllium, or silicon with an oxide layer on top, among others.
The bridge 50 is formed from an exposed portion of the buffer layer 68, and disposed upon the conductive layer 66. The second conductive layer 70 is disposed over the buffer layer 68. The second conductive layer 70, as explained above, typically extends across and forms an exposed surface of at least a substantial portion of the lands 42 and 44, but may be absent from all or a substantial portion of the bridge portion 50. The flyer layer 52 is then placed over the bridge portion 50. The buffer material 68 acts to prevents migration of the second conductive layer 70 into the material of the conductive layer 66 and vice versa. The buffer material 68 also acts to better adhere the flyer layer 52 on bridge portion 50 where the second conductive layer 70 is absent.
FIG. 4A is a top view of the diagram of FIG. 3 with the flyer layer 52 removed for clarity. FIG. 4B is a top view similar to FIG. 4A with the flyer layer 52 shown in circular dashed lines to indicate areas of adhesion inside the region bounded by circular dashed lines. The flyer layer 52 adheres to the substrate 54 in first adhesion regions 81. The flyer layer adheres to the bridge 50 in a second adhesion region 82. The flyer layer 52 adheres to the lands 42, 44 in third adhesion regions 83. The flyer layer 52 adheres to the bridge portion 50 in the adhesion region 82.
In use, the lands 42, 44 are connected to a suitable current source (not shown). When sufficient current, for example, several hundreds of amps, is applied through the lands 42, 44, the bridge member 50 vaporizes and is turned into a plasma. This plasma accelerates a portion of flyer layer 52 (“the flying plate”) away from the substrate 54 and towards an explosive (not shown). The shock of the flyer layer 52 striking the explosive detonates the explosive.
In general, the dielectric material forming the flyer layer 52 adheres well to the ceramic substrate 54 in the first adhesion regions 81, and to the bridge 50 formed from the buffer material 68 (FIG. 3) in the second adhesion region 82. However, since the lands 42, 44 are generally formed of a material selected for solder-ability, the dielectric material forming the flyer layer 52 may not adhere consistently to the lands 42, 44 in the third region 83, leading to variability of performance of the chip slapper 46. Furthermore, in chip slappers 46 where the exposed bridge portion 50 is formed of a conductor material, for example, if the buffer material 68 is omitted or if the second conductive layer 70 is not removed from the bridge 50, the dielectric material forming the flyer layer 52 may not adhere consistently to the bridge 50 in the second region 82. Therefore, there is a need in the industry to overcome the abovementioned shortcomings.